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Smyrna, TN, United States

Tantawi K.H.,Motlow College | Waddel E.,University of Alabama in Huntsville | Williams J.D.,University of Alabama in Huntsville
Journal of Materials Science

Little is known about photostructurable glasses when compared to quartz and the other glass families. This article investigates optical and thermal behavior of the two commercially produced Apex™ and Foturan™ photosensitive glasses in relation to their composition. A composition analysis is performed on the two glasses using Rutherford backscattering spectrometry, and UV spectroscopy. Cerium and silver were found to exist at higher concentrations in Foturan than in Apex glass. Difference in transmission in the 240-340 nm window is mainly attributed to the different concentrations of cerium and silver in the glasses. Infrared transmission in the range of 2.7-5.0 μm is improved following an annealing process. Structural stability over a different range of temperatures in the two photosensitive glasses is investigated, and is attributed to the silica content at the expense of lithium oxide. Raman spectroscopy shows that the UV-exposed-then-baked photosensitive glass, results in the formation of a uniform crystalline-phase lithium metasilicate with a preponderantly Q2 species. © 2013 Springer Science+Business Media New York. Source

Gaillard W.R.,University of Alabama in Huntsville | Tantawi K.H.,University of Alabama in Huntsville | Tantawi K.H.,Motlow College | Waddell E.,University of Alabama in Huntsville | And 2 more authors.
Journal of Micromechanics and Microengineering

Chemical etching and laser drilling of microstructural glass results in opaque or translucent sidewalls, limiting the optical analysis of glass microfluidic devices to top down or non-planar topologies. These non-planar observation topologies prevent each layer of a multilayered device from being independently optically addressed. However, novel photosensitive glass processing techniques in APEX™ have resulted in microfabricated glass structures with transparent sidewalls. Toward the goal of a transparent multilayered glass microfluidic device, this study demonstrates the ability to perform spectroscopy with optical fibers and microcuvettes fabricated in photosensitive APEX™ glass. © 2013 IOP Publishing Ltd. Source

Tantawi K.H.,Motlow College | Berdiev B.,University of Alabama at Birmingham | Cerro R.,University of Alabama in Huntsville | Williams J.D.,University of Alabama in Huntsville
Superlattices and Microstructures

This article presents the assembly and signal transduction of an artificial biological membrane suspended on a thin porous silicon template. The electrochemically-fabricated porous silicon membrane has average pore diameters in the range 0.50-2 μm and dimensions of about 200 × 200 × 3 μm3 and may be batch fabricated in large arrays for combinatorial testing. Biological membranes may be deposited on one or both sides of this template are fully accessible for studies using electrochemical impedance spectroscopy. Initial results using a two probe impedance measurement clearly show a significant impedance change between the porous silicon structure and the lipid bilayer. Furthermore, there is a clear reduction in the impedance of lipid bilayer when fused with a transmembrane ion channel protein. The photoluminescence and biodegradability properties of porous silicon in addition to lower cost and ease of fabrication make it superior over e-beam patterned silicon structures used in previous works, and thus suitable for in vivo monitoring. © 2013 Elsevier Ltd. All rights reserved. Source

Tantawi K.H.,Motlow College | Cerro R.,University of Alabama in Huntsville | Berdiev B.,University of Alabama at Birmingham | Williams J.D.,University of Alabama in Huntsville
Technical Proceedings of the 2013 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2013

This work presents a method to characterize the electrochemical properties of transmembrane ion channels and lipid bilayer membranes. The system is composed of a 3 μm thick porous silicon membrane with the epithelial sodium channel (ENaC) proteins fused into a lipid bilayer membrane (LBM) supported on the porous silicon layer. The LBM was composed of two synthetic phospholipids: 1,2-diphytanoyl-sn-glycero-3-phosphoserine and 1,2-diphytanoyl-sn-glycero-3- phosphoethanolamine. Electrical Impedance spectroscopy was performed from 0.1 Hz to 100 KHz. The electrochemically-fabricated porous silicon template had pore diameters in the range 0.2-2 urn. The LBM was formed by means of the Langmuir-Blodgett and Langmuir-Schaefer techniques, at a bilayer surface tension of 40 mN/m in room temperature. The electrolyte-PSi system showed on average a capacitance of about 9.76 μF/cm". The lipid bilayer membrane showed a capacitance of about 0.63 μF/cm2. The ENaC channels resulted in a capacitance of about 0.57 μF/cm". Source

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